Coupled defect-size effects on interlayer friction in multiwalled carbon nanotubes

Systematical molecular statics and dynamics simulations are performed on the interlayer friction and energy dissipation of biwalled carbon nanotubes of different chirality and size, with and without defects. The interlayer friction force of perfect bitube systems is strongly dependent on commensuration and independent of the tube length in incommensurate systems at very low temperature. However, the existence of defects can ruin the perfect-geometry controlled interlayer interaction and lead to a sharp increase in friction and energy dissipation rate. The oscillating energy dissipation rate increases monotonically even in an incommensurate bitube system with increasing tube length and defect density. The coupled effects of system registration, size, and defects are demonstrated, which can explain how an ultrasmooth nano-bitube system leads to a rougher longer tube system and provides a new mechanism for multiscale tribology. Simulations on the influence of attachments and terminal conditions at the end of the tubes show that H terminations lead to a higher rate of energy dissipation in a bitube oscillator than capped and freely open cores in the systems. The findings of these important effects can provide a fundamental understanding with which to create novel nanosystems from multiwalled carbon nanotubes.